1. Field of the Invention
The present invention relates to a display device and a display method suitable for application to a liquid crystal display and an organic EL (electroluminescence) display, for example, and particularly to display techniques that enable light reception in parallel with light emission.
2. Description of the Related Art
In related art, when a touch panel for allowing an operation by touching a display screen of a display device such as a television receiver or the like is formed on the display screen, the tough panel separate from the display device is put over the display screen.
As a constitution using a separate touch panel, there is for example a constitution having a thin transparent input detecting device affixed on a screen. This is a touch sensor using a conductive film. There are for example pressure-sensitive type devices detecting pressure, capacitance type devices changed by contact with a human body, and the like. In addition, there are devices referred to as an electromagnetic induction type, which allows a position to be input using a special pen. These devices have a structure in which the surface of a display panel has another special panel for position detection placed thereon.
While touch detection principles for these devices using the detection panel placed on the display panel are easy, a decrease in display quality inevitably occurs because some member is placed on the display panel. In addition, since a detection method is mainly a method of detecting a capacitance change, it is difficult to detect inputs at two or more positions simultaneously.
Touch panel systems in which no panel is added on the surface include an optical type. A combination of a light emitting element (light emitting diode or the like) and a phototransistor is arranged on an upper, a lower, a left and a right side of a panel. A position is detected on the basis of light blocked by a finger or the like. Such an optical type does not cause a decrease in display quality, but is not suitable for portable devices because of the large scale of the devices located around the periphery of the display device.
In order to eliminate the inconveniences of these touch panels in related art, devices have recently been proposed in which the screen of the display devices functions as a touch panel as it is without a separate touch panel being provided. Japanese Patent Laid-Open No. 2004-127272 (FIG. 5) discloses such a display device that performs light emission and light reception in parallel.
An example of such a display device that performs light emission and light reception in parallel is configured such that for example display (light emission) of light emitting elements for image display, which elements are arranged on a display surface, is made intermittently, a charge corresponding to received light is accumulated in the light emitting elements themselves in periods when the light emission is stopped, and the accumulated charge is read. As a display device that makes such a configuration possible, there is for example an organic EL display. In addition, it is proposed that when display elements themselves do not have a function of receiving light (accumulating charge) as in the case of liquid crystal displays, light receiving elements are arranged adjacent to the display elements and light is received by the light receiving elements in periods when display (light emission) is stopped.